This invention relates to bicycles or similar devices which are operated by manual turning of foot pedals in circular orbits. More particularly the invention relates to stroke adjuster attachments for selectively changing the diameter of the orbits which are traveled by the pedals in devices of this type.
The foot pedals of a bicycle or the like are mounted on two crank arms that extend in opposite radial directions from the rotary axis of a drive sprocket. In a conventional bicycle the crank arms are of equal length and the pedals are situated at the ends of the crank arms. Thus, in an unmodified conventional bicycle, both pedals must be traveled around orbits that are of equal diameter and which are of fixed size. This can cause significant problems for many bicyclists.
Smaller persons may have difficulty operating a bicycle having a pedal orbit that is proportioned for an adult of average size or, in extreme cases, may find that to be impossible. Operation of the same bicycle by persons who have unusually long legs may be uncomfortable. Other persons may have physical impediments that limit foot movement to a pedal orbit that is smaller than would normally be appropriate. In some cases only one foot may be subject to the impediment. In those cases, the orbit of one pedal should differ from the orbit of the other.
This problem has heretofore been addressed by a variety of stroke adjuster mechanisms which enable selective changing of the distance between a foot pedal and the rotary axis of the drive sprocket which the pedal turns. The pedal is detached from the bicycle crank arm and is reattached to a slidable member which can be positioned at any of a plurality of locations along the crank arm. Use of stroke adjusters of this kind as heretofore configured has been undesirably complicated as bicycle crank arms do not have a single standardized shape. Different crank arms have different sizes and configurations. This is most notably the case in the region of the crank arm which is closest to the rotary axis of the sprocket gear to which the crank arm is attached. Crank arms may have various different curvatures and configurations in that region.
Consequently, components of prior stroke adjusters which fasten the attachment to a crank arm are designed for use with a crank arm of a specific shape and in many cases are not easily attachable to crank arms having other configurations. Use of stroke adjusters would be facilitated and become more practical if the adjusters were compatible with diverse crank arms having a variety of different sizes and shapes.
The present invention is directed to overcoming one or more of the problems discussed above.